1. Field of the Invention
The present invention relates to an improved enameled wire and more particularly it relates to an enameled wire which can prevent the occurrence of smoking accidents of electric machinery such as a transformer, an electric motor, etc., (in particular, a small-sized transformer and a small-sized electric motor) in which the enameled wire is used. Furthermore, if necessary, the enameled wire of this invention can prevent the occurrence of smoking accidents, fire accidents, or electric shock accidents of electric machinery by such a mechanism in which the enamel layer or the insulration layer of the enameled wire is easily melted, when the enameled wire reaches a definite temperature, to short-circuit the wires and thus to fuse the wire at the portion which is not short-circuited.
2. Description of the Prior Art
Recently, smoking accidents, fire accidents or electric shock accidents by houshold electric articles such as televisions, etc., have become more and more frequent and thus it has strongly been desired to prevent these accidents. In response to such a desire, the safety regulations for electric and electronic equipment or articles have become severe in each country. This problem will be easily solved for the equipment of utilizing low voltage and low electric power of these types of electric and electronic equipment, but televisions, electronic ranges, etc., which use high voltage and high electric power have various disadvantages in preventing smoking accidents, fire accidents, or electric shock accident and design of this equipment to overcome these problems has been strongly demanded. According to the statistics for television receivers in the United States of America as an example of the occurrence of fire accidents and smoking accidents for the parts of such electronic equipment, accidents due to the transformer ranks first or occupies about 30 percent of all of the accidents and about half of these accidents arise in transformers and high-voltage circuits. Therefore, it has strongly been demanded that the electric circuits of such parts be automatically broken before the occurrence of [the ] fire or electric shock accidents without generating smoke when abnormal conditions with such electric or electronic equipment occur rather than to render such equipment or parts thereof simply flame retardant. For meeting such demand, transformer makers have attempted to achieve reliability in transformers at the occurrence of difficulties by employing a fusing system such as a bimetal system in the transformers as a safeguard against such. However, in this case, if, for example, the cost of a small-sized transformer for transistorized equipment is assumed to 100, the cost of the fuse used for the transformer becomes about 30 to 100, which increases greatly the cost of the equipment containing a fuse system, and further the employment of such a fuse system is also undesirable from the standpoint of space for the transistorized equipment.
In spite of the increase in cost, under the present conditions, manufacturers tend to employ such a fuse system in electric or electronic equipment to meet the severe safety regulations. The same is true for small-sized electric motors used for tape recorders, etc. Accordingly, it has been keenly desired to prevent the occurrence of smoking accidents and fire accidents in the case of an abnormal temperature increase due to over load, etc., without increasing the cost of the equipment.